Veggie mixture-Preheat oven to 375F. Over medium heat add 1/2 Tbsp oil to a hot pan and sauté onions for 15 minutes. You want the onions to slightly caramelized. Next add tomatoes, garlic, mushrooms, and a pinch of salt and pepper and cook for another 15 minutes. Add the chopped spinach and sauté for 2 minutes. Remove from heat.
Tofu filling-combine tofu, almond milk, nutritional yeast, baking soda, salt, pepper, and turmeric, in a blender or food processor. Blend until smooth.
Add the vegetable mix to a pre-baked pie crust or a well-oiled pan if making a crustless quiche. Pour the tofu mixture on top and gently combine.
Bake for 35-40 minutes. Let cool for 10 minutes before serving.